Lubricating sealing means for rotary combustion engines



May 3, 1966 E. HOPPNER ETAL LUBRICATING SEALING MEANS FOR ROTARYCOMBUSTION ENGINES Filed (kit. 10, 1963 3 Sheets-Sheet 1 Ill [sir/ grINVENTORS ERNST HOPPNER RqLF LECH LER @1259? HOFFMANN ATT'URNLY y 1966E. HOPPNER ETAL 3,249,094

LUBRICATING SEALING MEANS FOR ROTARY COMBUSTION ENGINES Filed Oct. 10,1963 5 Sheets-Sheet 2 INVENTORS 'l= l g z 2 ERNST HOPPN ER RQLF' LECHLERGUNTER HOFFMANN NEY y 3, 1966 E. HGPPNER ETAL 3,249,094

LUBRICATING SEALING MEANS FOR ROTARY COMBUSTION ENGINES Filed Oct. 10,1965 3 Sheets-Sheet 5 TE-7 141m IIIFJVENTORS ERNST HOPPNER RQLF LECH LERGUNTER HOFFMANN BY ATT NEY United States Patent 3 2495994 LUBRICATINGSEALING MEANS FOR ROTARY CGMBUSTION ENGINES Ernst Hiippner, Lindau(Bodensee), Rolf Lechler, Bad Friedrichshall-Kochendorf, and GiinterHoifmann, Neudenau (.l'agst), Germany, assignors to NSU MotoreuwerkeAktiengesellschaft, N eckarsulm, Germany, and Wankel G.m.b.H., Lindau,Germany Filed Oct. 10, 1963, Ser. No. 315,280 Claims priority,application Germany, Oct. 13, 1962, N 22,209 13 Claims. (Cl. 123-8) Thisinvention relates to internal combustion engines, in particular to thoseof the rotary piston type, and is directed to improved sealing meansbetween relatively moving parts of such engines.

In general, engines of this type comprise an outer body formed by aperipheral wall interconnected by a pair of parallel end walls therebydefining a cavity whose peripheral shape preferably is basically anepitrochoid. A rotatably mounted rotor is supported for eccentricmovement on a shaft within the cavity "and has a plurality ofcircumferentially-spaced apex portions with radially movable seal stripsmounted therein for sealing engagement with the inner surface of theperipheral wall, thereby forming Working chambers which upon relativerotation of the outer body and rotor vary in volume. An in take port isprovided for admitting a fuel-air mixture to the combustion zone of saidengine, and an exhaust port is provided for expelling the burnt gases.Any suitable method of igniting the fuel-air mixture may be used,whereupon the stages of intake, compression, expansion and exhaust maybe carried out. A lubrication'system for the engine shaft and bearingsgenerally includes means for supplying lubricating oil also to theinterior of the. rotor for cooling purposes.

A rotary combustion engine of the character referred to above isdescribed in US. Patent No. 2,988,065, granted June 13, 1961, to FelixWankel et al.

As is well known in the operation of internal combustion engines, it isnecessary to prevent the lubricating oil from leaking past the pistoninto the zone of the engine where combustion gases are present, in orderto minimize oil consumption and avoid fouling. Heretofore, in rotarycombustion engines of this type an oil seal ring has been mounted in therotor side walls for resilient sealing contact with the inner faces ofthe corresponding end walls of the engine housing. However, because ofpossible distortion of the housing side walls incident to highcombustion temperatures, and/or roughness or uneven character of thesewalls, the usual piston seal ring does not always make leak-proofcontact between the piston and housing. In such instances, oil lubricantmay pass into the operating chambers, especially during the inductioncycle. A further disadvantage of this arrangement is that this oil-sealring, which is in direct heatconducting relation to the piston, oftenincludes in part a non-metallic rubber-like material which deterioratesgradually at piston temperatures, thereby limiting the useful life ofsuch rings. Summarizing briefly, the usual oilseal rings interposeddirectly between the coacting walls of the piston and housing involvematerial difficulties that have not entirely been overcome.

A principal object of this invention therefore is to provide new andimproved lubricant sealing means for a rotary combustion engine of thecharacter described, wherein an oil sealing device is interposed betweenthe engine shaft structure and the piston for preventing leakage of oilfrom the transmission area past the piston into the operating chambers.

A further object of the invention is to provide in a preferred form newand improved sealing means wherein oil sealing ring structure is carriedby and rotatable with the shaft structure for directly engaging thepiston and avoiding the sealing difficulties previously referred to.

In particular, the present invention provides primary and secondary oilsealing means, both preferably carried by the conventional shafteccentric. The primary sealing means engages directly the piston sidewalls for sealing the shaft, transmission and bearing areas containingthe pressurized lubricant with respect to the piston, and the secondarysealing means likewise carried by the eccentric (or cam) makes ashaft-housing seal for the comparatively low-pressure exhaust lubricant,thereby preventing leakage of lubricant along the housing side walls tothe piston along a path lay-passing the shaft piston seal.

The invention will be more fully set forth in the following descriptionreferring to the accompanying drawings, and the features of novelty willbe pointed out with particularity in the claims annexed to and forming apart of this specification.

Referring specifically to the drawings:

FIGURE 1 is a simplified sectional view of a rotary combustion engine ofthe type to which the present invention is applicable;

FIGURE 2 is a detailed sectional. view of the engine taken generallyalong the line 2-2 of FIGURE 1 showing application of the inventionthereto;

FIGURE 2A is an enlarged detail view of the piston seal shown in FIGURE2;

FIGURE 3 is a sectional view taken along the line 3-3 of FIGURE 2showing the piston drive and shaft eccentric structure of the engine;

FIGURES 4, 5 and 6, 7 are separate detail views of the seal discs ofFIGURE 2 that are mounted on opposite sides of the engine shafteccentric; and

FIGURES 8, 9 and 10 are detail views in section showing alternativeforms of the piston seal.

In FIGURES l and 2 there is shown a rotary combustion engine having anouter body or housing generally designated at 1 composed of a pair ofend walls 3 and 4 interconnected by a peripheral wall 2. The housingdefines a cavity therein having a transverse axis M1. As shown, forexample in FIGURE 1 the profile of the inner wall 2 is basically atwo-lobed epitrochoid. A shaft 6 is rotatably mounted in the housingco-axial with the axis M1 and has an eccentric portion 7 formed thereon.A rotor 8 is rotatably mounted on the eccentric and has threecircumferentially spaced apex portions 12, FIG- URES l and 2, which arein sealing cooperation with the inner surface 2 to form a plurality ofworking chambers 5 which upon relative rotation of the wall 2 and rotor8 vary in volume. Seal strips 12 as indicated are mounted in each apexportion and extend from one end face of the rotor to the other end face,FIGURE 2, for continuous sealing engagement with the inner surface 2,thereby sealing the working chambers 5.

End face seals 3 and 4' are also provided in each end or side face ofthe rotor and are in sealing engagement with the housing side walls 3and 4 at surfaces 311 and 4a respectively, to prevent leakage of thegases from the working chambers 5 past the rotor in known manner.

A suitable bearing 9 is supported in the rotor 8 for rotativelysupporting the rotor on the eccentric 7. Suitable bearings 6a and 6b arealso mounted in the end walls 3 and 4. as shown in FIGURE 2 forsupporting the rotating shaft 6 in the housing.

The rotor (piston) drive connection with the shaft comprises anexternally-toothed gear or pinion 10 that is secured to the shaftjournal box at the wall 4 in meshing engagement with aninternally-toothed gear 11 which constitutes an end-portion of the rotorinner bearing ring 11'.

The gears and 11 serve to r-otatively position the rotor with respect tothe epitrochoidal surface of the peripheral wall 2. In the embodiment,FIG. 1, illustrating a two-lobed epitrochoid and a threelobed rotor, theratio of rotation of the eccentric 7 and its shaft 6 with respect to therotor is 3:1, i.e., for each rotation of the rotor about its axis M2,which corresponds to the center of the eccentric 7, the eccentric andshaft 6 rotate three times around the shaft axis M1. The eccentricity Eof the cam 7 represents the piston throw or stroke.

Illustration of the other engine operating features including a fuel-airmixture intake port, ignition or spark plug and exhaust port for thecombustion gases is unnecessary for a complete understanding of theinvention and therefore is omitted; an adequate description thereof isin the Wankel et al. Patent 2,988,065 referred to above.

The lubrication system for the essential bearings and gears includingthe main shaft bearings 6a and 6b, the piston-eccentric bearings 9 andthe piston position gearing 10-11, comprises interconnecting passages inthe housing, shaft structure and piston hereinafter described throughwhich a lubricating medium referred to as oil, is circulated. The oil isapplied as indicated by direction arrows so as both to lubricate themain shaft bearings and the transmission and drive parts, and also tocool the interior of the piston.

In order to confine the oil to the shaft and transmissiondrive areas andprevent its leakage past the piston into the operating chambers 5, themain oil seal is made essentially between the shaft eccentric and thepiston itself, rather than between the engine side walls and piston according to prior practice as explained above. To this end, there issecured to the shaft eccentric 7 at least one seal-carrying member 14 or15, as the case may be, located between one side of the eccentric andthe corresponding housing side wall. Specifically, the member 14 (or 15)may be of disc-like form having its center coincident with the center ofthe eccentric 7 which also defines the axis of rotation M2 of thepiston. As shown in FIGURE 3, the disc 15 is cut away at 21 to form acrescent for rotation clearance at the piston internal ring gear 11,companion fixed gear 10 and shaft 6.

Although as will be apparent, a single disc may be used for sealingpurposes at one side of the piston in accordance with the invention (thepiston in such case having a conventional ring seal at its opposite sideand being axially biased toward that side of the housing) a preferredconstruction includes two discs 14 and 15 secured as by bolts toopposite sides of the eccentric, FIGURES 2 and 3, for rotation with-theshaft 6. The disc peripheries are located respectively opposite a recesswall 18 formed at each side of the piston, FIGS. 2 and 2A.

As the annular seals carried by the discs for wiping the piston sidewalls are essentially similar, a description with special reference toFIG. 2A of the seal ring 16 carried by the disc 14 will be suflicient.This ring is composed of a suitable metal and has a generally U-shapecross-section. It is retained within the outer part of the disc 14 by atransverse flange thereof 14', so as to be concentric of the piston axisM2 and movable axially, -i.e., toward and away from the piston side wall80. The ring is resiliently biased toward the piston wall by an annularspring 17 positioned between the inner side of the disc and the ring asshown. The ring may have an annular shoulder on its inner periphery atthe disc side for retaining the spring.

A fluid-tight seal between the ring 16 and disc flange 14 is provided byan O-ring 16a of rubber-like material enclosed under compression withinthe U of the ring. Accordingly, the ring 16 which is biased laterally tomake annular wiping engagement with the adjacent piston side wall 80completes a seal between that piston wall surface 8a and the shafteccentric and disc structure.

The normally oil-containing passages and spaces referred to above forlubricating and cooling purposes are formed in part by the sealing discs14 and 15. As shown 4 in FIGURES 2 and 3, the oil enters the housing bya passage a formed inthe end wall 4 and communicates with the gearing10-11 through an annular passage b formed in the corresponding mainbearing housing. The cut-away part of the disc 15 at 21 admits oil frompassage b to all the gearing 1041 during rotation of the piston aroundthe fixed gear 10. From passage b the oil flows through radiatingpassages c formed in the disc 15 to the piston-eccentric bearings 9, andthrough passage 0! in the ring gear and piston into the hollow pistoncooling pas-' sage e.

The disc 15 is provided with a circular flange or hub portion 22a,FIGURES 2 and 5, that makes an oil seal at 22b with the housing end wall4 as shown, thereby sealing the piston at its side 8b from oil in theannular passage b.

The oil outlet from the piston cavity e includes another passage 1 inthe piston and ring gear which communicates with a generally circularspace g formed in part between a crescent-shape portion 14' of the disc14, FIGURES 2, 6 and 7, and the surrounding wall of the piston at itsinner-periphery. This space in turn opens into the cylindrical hubextension 22 of the disc which extends over a smaller diameter hub 3'formed on the bearing housing and constituting part of the engine sidewall. The space therebetween defines an annular passage h leading to theoil exhaust port k.

For the purpose of sealing the disc hub 22 and hence the oil passage 11,with respect to the housing wall 3, the hub which is rotatable withinthe end wall 3, is provided, as in the case of the hub 22 of disc 15,with an oil seal, such as spiral grooves 23 formed in the outer surfaceof the hub. Thus, oil from the shaft area is prevented from leaking intothe clearance space between the housing side wall 3a and that side ofthe piston.

Alternative forms of seals used according to the invention are shown byFIGURES 8, 9 and 10. In FIG- URE 8, a resilient seal ring 16 is carriedby disc 14 for example, within an annular groove 16" and is biased bysuitable spring means axially outward rather than inward, to make thepiston seal. For this purpose a metal companion ring or annulus 25overlapping and surround ing the disc periphery is mounted on the pistonitself to form an extension of its side wall along the housing wall.Specifically, the ring has a radially extending flange 26 with are-entrant edge 26' that fits within 2. corresponding groove in the disc14 to form a supplemental labyrinth-type seal. The annular clearance gap27 between the disc 14 and ring- 25 is in communication with theoilcooling space e in the piston and slants radially outward as shown.Accordingly, oil from the passage 2 tending to enter the clearance gapis flung back into the piston cavity by centrifugal force due to thehigher rotative speed of the disc 14. Oil from the piston space e isthereby prevented from leakage past the disc into the piston-housingclearance and so into the engine operating chambers 5.

In FIGURE 9, the sealing ring 16' of FIGURE 8 is dispensed with and inlieu thereof a so-called gap-seal is used. Here, the disc 14 and pistonring 25 have close tolerance clearance surfaces that may have agenerally Z-shape form as shown. The radially extending part 28 of theclearance gap has a minimum length H to prevent leakage of oil from thepiston cavity e past the disc. This length depends on engine designfactors affecting the centrifugal force available to force back oil intothe piston cavity, including the maximum oil level in the piston cavity,the spacing of the radially extending outer end of the gap from theeccentric (disc) axis of rotation M2, and the piston throw E. A furtherconsideration is that oil entering the radial passage 28 be given tomaximum extent the rotative speed of the disc. To this end, theaforesaid tolerance should be as small as possible and the gap surfacearea of the higher speed disc be made rough and that of the lower speedpiston ring 25 be made smooth.

FIGURE shows a variation of the gap-seal wherein labyrinth sealingbetween the disc 14 and piston at 29 is used. Here, the piston ring andthe disc 14 overlap radially and have a staggered tongue and groovemating configuration to form a labyrinth along the clearance gap.

Although the disc-piston sealing action is herein described as generallyaxial, it will be understood that radial sealing between the discs andpiston is contemplated as being within the spirit of the invention.

It will also be understood that the discs 14 and 15, though preferablyconcentric with the piston axis of rota.- tion M2, may have a slighteccentricity with resepct to this axis where the seal of FIGURE 2, forexample is used. This eccentricity can be advantageous for widening theseal-wiped area of the piston wall where the seal tends to abrade andwear a groove in the piston.

It should be understood that this invention is not limited to specificdetails of construction and arrangement thereof herein illustrated, andthat changes and modifications may occur to one skilled in the artwithout departing from the spirit of the invention.

What is claimed is:

1. In an internal combustion engine of the rotary piston type having ahousing, a piston mounted for eccentric rotation within said housingsuccessively to form with said housing walls variable-volume operatingchambers, a rotatable power output shaft mounted in said housing, andtransmission drive means between said piston and shaft provided withcontinuous lubrication, improved means for preventing passage of thetransmission lubricant into the aforesaid operating chambers comprisingmeans secured to said shaft for rotation therewith, and sealingstructure concentric of the axis of rotation of the piston interposedbetween said shaft-secured means and a side wall of the piston andmounted in one of them for preventing leakage of the lubricant past thepiston side wall into said operating chambers.

2. Apparatus as specified in claim 1 wherein the shaftsecured means is arigid member, generally in a plane parallel to a side wall of thepiston, said member and a generally similar member being rotatable withthe shaft and extending along opposite side walls respectively of thepiston, each member having means for retaining its respective sealingstructure for engaging a corresponding side wall of the piston.

3. Apparatus as specified in claim 1 wherein the shaftsecured means alsohas a hub portion surrounding the shaft for engaging in sealing relationthe engine housing side wall for sealing the lubricant within that partof the housing enclosing the shaft.

4. Apparatus as specified in claim 3 wherein the hub portion of theshaft-secured means is rotatable within a cylindrical portion of thecorresponding housing side wall and has oil sealing grooves formed atthe outer surface thereof to constitute a seal between the shaft andhousing side wall.

5. Apparatus as specified in claim 1 wherein the sealing structurecomprises a sealing ring mounted in said shaftsecured means and biasedin a direction parallel to the shaft axis into sealing engagement with aside wall of the piston.

6. Apparatus as specified in claim 5 wherein the shaftsecured means is adisc concentric with the piston axis of rotation and rotatable with theshaft, said disc having a peripheral flange portion formed to retainsaid sealing ring in sealing. contact with the piston.

7. Apparatus as specified in claim 5 wherein the sealing ring iscomposed of metal and a resilient non-metallic ring is mounted betweenthe metal ring and shaft-secured means for sealing the engaging surfacesthereof.

8. Apparatus as specified in claim 5 wherein the piston has an annularmetal sealing annulus forming an extension of the piston side walloverlapping and surrounding in close tolerance the sealing ring, and thesealing ring is biased axially outward into engagement with saidannulus.

9. Apparatus as specified in claim 1 wherein the sealing structureconstitutes a split seal ring forming a narrow clearance slot extendingradially with respect to the piston axis whereby centrifugal force dueto rotation of said shaft-secured means tends to prevent passage oflubricant through said slot toward the shaft.

10. Apparatus as specified in claim 1 wherein the sealing structurecomprises an annular metal sealing annulus forming an extension of thepiston side wall, and the shaft-secured means is a disc, the peripheralportion of said disc being surrounded in close tolerance by said annulusto form a gap-seal and the disc and annulus surfaces defining agenerally Z-shape gap having a radially extending portion through whichleakage of oil toward the shaft is opposed by centrifugal force incidentto rotation of said disc.

11. Apparatus as specified in claim 1 wherein the sealing structureconstitutes a split-seal ring, one part of which is attached to a pistonedge at the housing side wall, the other part being attached to theshaft-secured means, the clearance gap between said parts defining aclose tolerance labyrinth.

12. In an internal combustion engine of the rotary piston type having ahousing, a piston mounted for eccentric rotation within said housingsuccessively to form with said housing walls variable-volume operatingchambers, a rotatable power output shaft mounted in said housing, andtransmission drive means including an eccentric between said piston andshaft provided with continuous lubrication, a member secured to saideccentric for rotation therewith, and sealing means interposed axiallybetween a peripheral part of said member and a side wall of the pistonand mounted in one of them to preclude leakage of lubricant from theshaft and transmission areas past the piston at said side wall into saidoperating chambers. I

13. Apparatus as specified in claim 12 wherein the eccentric-securedmember is a disc secured to the eccentric at one side thereof andextends adjacent to a piston side wall, and the sealing meansconstitutes a ring-type seal surrounding the shaft concentrically of thepiston axis of rotation and mounted between the respective side walls ofthe disc and piston to be sealed for making, together with said disc, anaxial seal between the shaft and the aforesaid piston side wall.

No references cited.

SAMUEL LEVINE, Primary Examiner.

F. T. SADLER, Assistant Examiner.

1. IN AN INTERNAL COMBUSTION ENGINE OF THE ROTARY PISTON TYPE HAVING AHOUSING, A PISTON MOUNTED FOR ECCENTRIC ROTATION WITHIN SAID HOUSINGSUCCESSIVELY TO FORM WITH SAID HOUSING WALLS VARIABLE-VOLUME OPERATINGCHAMBERS, A ROTATABLE POWER OUTPUT SHAFT MOUNTED IN SAID HOUSING, ANDTRANSMISSION DRIVE MEANS BETWEEN SAID PISTON AND SHAFT PROVIDED WITHCONTINUOUS LUBRICATION, IMPROVED MEANS FOR PREVENTING PASSAGE OF THETRANSMISSION LUBRICANT INTO THE AFORESAID OPERATING CHAMBERS COMPRISINGMEANS SECURED TO SAID SHAFT FOR ROTATION THEREWITH, AND SEALINGSTRUCTURE CONCENTRIC OF THE AXIS OF ROTATION OF THE PISTON INTERPOSEDBETWEEN SAID SHAFT-SECURED MEANS AND A SIDE WALL OF THE PISTON ANDMOUNTED IN ONE OF THEM